Foodstuffs consist of an extremely broad spectrum of constituents. These include                nitrogen-containing (proteinaceous) compounds (e.g. one or more free amino acids or their derivatives, protein hydrolysates, intact whole proteins, or a combination of these) plus vitamins, including amino nitrogen containing vitamins, and their derivatives, plus other, non-amino nitrogen-containing compounds, e.g. ammonium compounds such as ammonium sulphate        carbohydrates, including                    reducing sugars, e.g. glucose (also known as dextrose), fructose (also known as levulose) and 5-carbon or pentose sugars such as xylose, and other aldehyde containing compounds which may be found, for example in flavouring agents            non-reducing disaccharide sugars (e.g. sucrose) which may be hydrolysed to produce the reducing sugar moiety, this reaction being promoted by the presence of moisture and elevated temperatures.                        
Over time, in the presence of moisture, and in even moderate heat (i.e. at temperatures above the freezing point of water), the Maillard reaction occurs.
The Maillard reaction is a reaction consisting of an a nucleophilic attack by a free amino group present in a protein, a peptide or an amino acid on an aldehyde group of a reducing sugar. The reaction products further cause a series of reactions with other proteinaceous amino groups, thereby to form a brown material and to cause a crosslinking between proteins. Historically, Maillard reported in 1912 that a mixed solution of an amino acid and a reducing sugar, when heated, is coloured into brown (L. C. Maillard, Compt. Rend. Soc. Biol., 72, 599 (1912)) and, since then, the reaction is called Maillard reaction. In foodstuffs the Maillard reaction typically comprises the interaction of the nitrogen compounds with the aldehyde groups of reducing sugars or other carbonyl compounds.
In some instances, the browning of a Maillard reaction is desirable, for example with butterscotch confections, caramel, cooked meats, etc. In other instances this reaction is undesirable. For example the Maillard reaction can be problematic in some baked food items such as gratin and cakes in which this browning reaction is not easily controlled. This may result in the attractive brown colour becoming too dark and producing black blisters. Clearly this is not desirable.
Furthermore the Maillard reaction can be problematic in the production of foodstuffs containing a dairy product, in particular cheese, which are cooked at a high temperature. In the area of pizza production there is a pronounced Maillard reaction from the cheese spread on top of the pizza. In the present specification and indeed in the art pasta fileta is referred to as mozzarella.
Many pizza manufacturers bake pizza at temperatures>260° C. At these high temperatures the propensity of the cheese to brown excessively has become a particular concern to the mozzarella industry because the mozzarella manufacturers must deliver cheese that will not make black blisters and brown areas when baked at these high temperatures.
The browning effect from mozzarella cheese is typically caused by residual amount of reducing sugars lactose and galactose left from the cheese production. Therefore many attempts to reduce the browning reactions of mozzarella have been based on attempts to reduce the levels of these sugars, and in particular the level of galactose, in the cheese.
In the traditional manufacture of mozzarella, during normal processing conditions, the fermenting micro-organism ferments only the glucose part of lactose and thus releases galactose into the medium. The cheese is subsequently washed during the manufacturing process, however, typically galactose and lactose remain in the cheese in an amount of 0.3 to 0.5 wt. %. Dr. Norman Olson, Dairy Record, June 1983, p. 112-113 has discussed that the degree of browning of mozzarella is related to the free amino acids and sugar concentration in the cheese, and the browning can be prevented by removing the reactants—usually sugar. He also refers to very strong correlation coefficient between galactose and colour levels of baked cheese. Many attempts to reduce the level of galactose and lactose in mozzarella are mentioned in the literature.
U.S. Pat. No. 3,531,297 discloses a process for manufacturing mozzarella comprising the step of soaking the curd in warm water to extract lactose from the curd, and thereby reduce the final lactose content of the cheese. In general, the lower the lactose content of the final mozzarella, the less tendency there is for the cheese to blister, burn, or char when it is subjected to high temperature baking.
While the process of U.S. Pat. No. 3,531,297 was used extensively on a commercial basis in the United States, and was a desirable commercial process, it does have certain disadvantages. The large curd soaking tanks add to the equipment and plant space costs, and the used soak water, which contains lactose, lactic acid and other substances, can add considerably to the waste disposal burden of an operating plant. Another limitation of the process of U.S. Pat. No. 3,531,297 is that the entire processing operation from the cheese vat to the mixer must be carefully timed, sequenced, and carried out on a substantially continuous basis. In practice, this means that the operators of the plant must almost immediately carry out the mixing of the cheese on the completion of the curd soak.
U.S. Pat. No. 4,085,228 discloses a low-moisture mozzarella prepared using a standard starter culture plus an additional culture selected from Pediococcus cerevisiae, Lactobacillus plantarum, Streptococcus faecalis, Streptococcus durans, and Lactobacillus casei, or mixtures thereof. Although the cheese is made by the usual processing steps, the cheese product has a reduced lactose sugar (and/or its monosaccharide derivatives) content due to the added culture, which metabolises residual lactose during a cold temperature holding at the end of the process. According to U.S. Pat. No. 4,085,228 the resulting cheese has improved properties for the manufacture of pizza, being substantially non-burning and having improving melt, flavour, and colour characteristics. However, the combination of two or more starter cultures makes the mozzarella cheese production more complicated and moreover, still the cheese will still contain minor amounts of galactose and lactose, which can take part in a Maillard reaction.
Mukherjee, K. K.; Hutkins, R. W. Journal of Dairy Science 1994, 77(10) 2839-2849 have shown that the use of a galactose-fermenting, galactose non-releasing micro-organism as a starter culture can produce of low browning mozzarella cheese. Galactose level below 0.1% in the mozzarella cheese was obtained by using selected micro-organism.
According to M. A. Rudan and D. M. Barbano, 1977 J. Dairy Sci 81:2312-2319 the problem related to too much browning and scorching of mozzarella is more pronounced when using low fat cheese (for example cheese containing 0.25-5.8% fat) rather than using a full fat cheese (for example 21% fat). It is discussed that the problem of over-browning is caused by the cheese surface drying too fast which results in scorching. In Rudan et al. the problem was reduced by spraying a layer of vegetable oil on the mozzarella.
In a review A. H. Jana, Indian Dairyman 44, 3, 1992, p. 129-132 mentions the problems with browning of cheese on baked pizza. It is disclosed that the problem is associated with residues of galactose and lactose in the cheese. A number of measures are disclosed to minimise the problem by controlling the level of galactose. These measures include:                use of specific combinations of Streptococcus and Lactobacillus bacteria which are able to ferment galactose. This will reduce the level of galactose in the cheese.        improved washing of the curd with hot water 60-80° C. during the final heating stage.        draining of the curd at pH>6.3 resulting in more of the remaining lactose and galactose being fermented.        moderating the processing temperature in the manufacture of processed mozzarella cheese.        prompt cooling of mozzarella cheese after moulding, leading to controlled levels of galactose in the cheese.        reducing the brining period thus avoiding excess salt in the water phase and allowing the lactic starter to ferment more of the residual sugar.        storing the cheese for a minimum period to reduce the proteolytic formation of free amino groups which are able to react with galactose.        
Many of the measures to minimise excessive browning mentioned by A. H. Jana are based on very strict process control or process modifications which are difficult to handle and/or may increase cost or decrease yield.
The addition of enzymes to cheese during the production thereof is known from the art. For example U.S. Pat. No. 5,626,893 teaches the use of glucose oxidase as an oxygen scavenger in anticaking agent for cheese.
The present invention alleviates the problems of the prior art.
Some aspects of the invention are defined in the appended claims.